Pyramid Structure Makes Better PHOLEDs

Photonics SpectraSep 2014
Arranging phosphorescent organic light-emitting diodes (PHOLEDs) into a pyramid shape can enhance their efficiency, making them brighter and more productive.

PHOLEDs are an efficient alternative to traditional incandescent lighting, but their efficiency is typically short-lived when they need to shine brightly.
Researchers at the University of Michigan have discovered a way to change that, simply by arranging them into a pyramid shape.

Light emission from PHOLEDs in a pyramid shape (left) has shown higher efficiency and brightness than conventional flat, four-sided concentrators (right). Images courtesy of Light: Science and Applications/University of Michigan.
Such light-emitting concentrators use significantly less electricity than conventional PHOLEDs, the researchers said.

“Achieving extra brightness from the conventional, flat design is inefficient and shortens the device lifetime,” said Jaesang Lee, a Michigan doctoral student in electrical engineering and computer science. “However, if we integrate our PHOLEDs into a pyramidal shape, we are able to achieve the equivalent, concentrated brightness at a much lower electrical current.”

PHOLEDs are naturally reflective, so when positioned into a pyramid-like structure, they emit, concentrate and utilize all light that is captured throughout. In their study, the researchers found that this new structure consumed about three times less electricity than when the PHOLEDs are arranged in a flat square.

PHOLEDs act as a light-emitting concentrator. They use significantly less electric energy than conventional light sources.
The new structure also demonstrated illumination that was three times brighter than the flat configuration, at the same electrical current strength.

“My hope is that OLEDs will deeply penetrate all aspects of the lighting market because they’re very efficient, very attractive, and, as people accept them, it will take a load off the electricity grid,” said lead researcher Dr. Stephen Forrest, Michigan’s William Gould Dow collegiate professor in electrical engineering.